Dewaxing system



April 20, 193 7.

R. E. WILSON DEWAXING SYSTEM Filed Aug. 31. 1931 Imemwm Robe/rtEWil/zw'n,

b3 3% KM Patented Apr. 20, 1937 UNITED STATES PATENT OFFICE DEWAXIN GSYSTEM Indiana Application August 31, 1931, Serial No. 560,346

8 Claims.

This invention relates to a dewaxing system and it pertains moreparticularly to a system for using liquefied light hydrocarbons such aspropane and butane as a diluent and refrigerant for 5 removing wax fromviscous lubricating oils to lower their pour points.

The object of this invention is to provide an improved dewaxing systemwhich will be more efficient than those heretofore used, which willavoid the necessity of unduly high pressures and which will increase therate of dewaxing and decrease the cost thereof. A further object is toprovide an improved refrigerating system which is particularly adaptedto the dewaxing of viscous pe- 5 troleum oils. Other objects will beapparent from the following detailed description.

It has been found that liquefied light hydrocarbons, such as propane,butane and, perhaps, pentane, are remarkably effective as diluents inthe dewaxing process because they result in improved wax crystalformation and because of their low specific gravity and viscosity. It isusually necessary to dissolve the wax in the liquefied hydrocarbondiluent prior to the chilling step, and this solution sometimes requirestemperatures as high as 125 to 150 F. At these temperatures the vaporpressure of the lighter components of the diluent mixture will be about300 or 400 pounds which requires costly apparatus and which isobjectionably hazardous. In practicing my invention I avoid the use ofthese high pressures by maintaining my refrigeration cycle separate anddistinct from my diluent cycle, so that the light vapors which areevaporated to effect the refrigeration are not subjected to hightemperatures. At

the same time these light hydrocarbons are present in the refrigeratingchamber in liquid form so that they have a. pronounced effect on theproper crystallization of the. wax, and permit the refrigeration cycleto be carried to quite low temperatures without using substantialvacuum.

In the accompanying drawing I have illustrated the layout of my improvedsystem by means of a flow sheet on which the apparatus isdiagrammatically shown.

In my system I utilize what I will call a butane cycle and a propanecycle. It should be understood that the expression butane as used hereinand in the following claims refers to hydrocarbons or hydrocarbonmixtures having approximately the vapor pressure of butane, and thatthis mixture might contain pentane, isobutane, small amounts of propane,etc.; generally it may be described as a liquefied light hydrocarbonhaving a vapor pressure of about 30 to 40 pounds per square inch at F.Likewise, the expression propane refers to the lighter components, andalthough it preferaby consists chiefly of propane, it may also containquantities of ethane, isobutane, butane, etc.; generally speaking it maybe defined as a 5 liquefied light hydrocarbon having a vapor pressure ofabout to at 70 F. In my system there is an equilibrium between thelighter components which are removed by the flash chamber, and theheavier components which act as a dilu- 10 ent and which are removedfrom the oil by distillation; the vapors removed from the refrigeratingchamber are hereinafter called propane and those removed from the oil bydistillation are called butane. 15

The oil to be dewaxed may be a heavy petroleum distillate or a steamrefined residue, it being understood, of course, that different amountsof diluent will be required for oils of various compositions,viscosities, etc. In my preferred ex- 20 ample I will describe thedewaxing of a heavy lubricating oil which is commonly known as motorbase stock. This oil may be produced from Mid- Continent crude petroleumand it preferably has a fiash point of about 470 F. and viscosity at 25210 F. of about '70-'75 seconds Saybolt. It may be a residual treatedsteam refined oil or it may be a treated overhead lubricating stock, theinvention being particularly applicable to the latter case becauseoverhead lubricants of this type 30 cannot be readily dewaxed by othermethods.

In practicing my invention about 7 parts by volume of butane fromstorage tank it are conducted through pipe ll, valve l2, pump l3 andpipe It to mixer I5 wherein it is mixed with about three parts ofwax-bearing oil (motor base stock) which is introduced through pipe l6and valve H. The temperature of the incoming oil may be high enough toeffect complete solution of the wax in the butane in mixer It, orseparate heating 4U means may be used to raise the temperature in themixer to about to F. The butane solution is then introduced by pipe l8into exchanger it, where it is cooled by water from pipes ill to normaltemperatures (about 70 F.) 45 after which it is conducted through pipe2! and reducing valve 22 to refrigerator or chill chamber 23.

The propane is introduced into the solution from storage tank 24 bymeans of pipe 25 and 5 valve 26 or by means of pipe 21 and valve 28,preferably the latter. It should be noted that the propane is added tothe solution after the solution has been cooled so that the propane willnot exert an undue pressure on the system. The 55 amount of propaneintroduced is sufllcient to cause the refrigeration of the diluentmixture to about 20 F.

The propane vapors are removed from chill chamber 23 by pipe 29,compressed by pump Ill and conducted by pipe 3| to cooling coils 32preferably immersed in a water-cooled bath 33. The propane pressure maybe about 120 to 150 pounds in coils 33, and at about 70 it is condensedand returned by pipe 34 to storage tank 24.

The chilled oil mixture and wax crystals form a slurry which iswithdrawn from base of chamber 23 by pipe 35 at about -20 F. This liquidis preferably forced through pump 35 or by fluid pressure through pipe31 to filter 38 wherein the Wax is removed. The butane oil mixture thenpasses through pipe 39, heat exchanger 40 and pipe 4| to boiler 42 whereit is heated to a temperature high enough to drive off the butanevapors. These vapors are withdrawn from the boiler through pipe 43, arecooled in exchanger 40 and are then passed by pipe 44 to anotherexchanger 45 which is cooled by suitable fluid introduced through pipe46. Condensed butane is conveyed from exchanger 45 through pipe 41,valve 48, pipe 49 and pipe 50 back to butane storage tank Ill.

Since the oil in boiler 42 was heated under pressure I introduce itthrough pipe and reducing valve 52 and pipe 53 into flash drum 54 whichis maintained at low pressure, preferably atmospheric. Suitableauxiliary heating or stripping means may be employed in this drum ifnecessary, but when butane is used as a diluent the oil leaving throughflash drum 55 is usually quite satisfactory from the standpoint of flashand pour points.

Butane from the top of flash drum 54 is circulated through pipe 56,compressed by pump 51, passed through condenser 58 (cooled by a fluidintroduced through pipes 58) and finally returned by pipes 80 and 50 tobutane storage tank I.

From the above description it will be seen that I avoid heating thepropane to temperatures materially above room temperature and therebyavoid the high pressures which would be developed if the propane wereinitially mixed with the waxy 01]. At the same time I obtain theadvantage incident to the use of propane in the wax separation bath andI obtain a rapid cooling without the necessity of a high vacuum and Iavoid the use of. unduly high temperatures and pressures.

While the above disclosure refers to the use of butane as a diluent, itis understood that I do not limit myself to butane or to liquefied lighthydrocarbons for this purpose. Excellent results may be obtained by theuse of wax antisolvents. such as a mixture of two-thirds parts benzoland one-third acetone, or any of the following mixtures:

Per cent Acetone 33 Isopropyl ether 25 Benzol 42 Per cent Benzol 41Normal butyl alcohol 59 Per cent Bennol 45 P011101 20 Methyl formats: 35

Per cent Benzol 47 Ethyl formate 53 Per cent Butyl acetate 100 Butylformate 100 Isopropyl ether 100 The above mixtures are exemplary only ofthe various antisolvents which may be used in practicing my invention.By using the propane or equivalent light hydrocarbon refrigerants, Iobtain unusually low pour points and at the same time I can obtainunusually high filter rates because the liquefied light hydrocarbonappears to have a marked influence on the crystal formation of the wax.

While I have disclosed a preferred embodiment of my invention, it isunderstood that I do not limit myself to the details therein set forthexcept as defined by the following claims, which should be construed asbroadly as the prior art will permit. It should be noted, for instance,that settling or centrifuging may be used instead of filtering toseparate the wax from the diluted oil. Other modifications will beapparent to those skilled in the art.

I claim:

1. The method of dewaxing a viscous petroleum oil comprising, dissolvingsaid oil at a temperature of about 140 F. in a light hydrocarbon diluentof higher boiling range than propane, cooling said mixture to atemperature of about 70, adding liquefied propane to said cooled mixturewhereby the propane becomes an efi'ective part of the diluent,vaporizing said propane in situ to effect refrigeration of the diluentoil mixture and the crystallization of wax therefrom. compressing,condensing, and reintroducing said propane for effecting refrigerationand diluting in the chilling step, separating said wax from said chilledmixture, recovering the diluent from said oil and returning it to bemixed with more wax-bearing oil out of contact with said propane.

2. The method of dewaxing a viscous hydrocarbon oil which comprisesdissolving a waxbearing oil with a diluent at a high, wax-dissolvingtemperature, cooling said mixture. introducing a liquefied normallygaseous refrigerant of lower boiling range than the diluent and of lowerboiling range than butane into said cooled solution whereby itsupplements the diluent effect in the wax crystallization step,vaporizing said refrigerant to effect a chilling of said mixture wherebywax is caused to crystallize therefrom, mechanically removing saidcrystallized wax from said diluted oil, recovering said diluent andreturning it to storage for reuse, and separately recovering saidrefrigerant and returning it to a separate storage for reuse.

. 3. The method of claim 2 wherein the diluent is a light hydrocarbon.

the use of normally gaseous hydrocarbon diluentrefrigerant mixtureswhich comprises employing separate diluent and refrigerant cycles withan evaporative cooling none common to both cycles,

8.11: a dewaxins system. a heated mixing chamber, a cooler, a chillingchamber, a refrigerant storage, means for introducing a suitable diluentand a wax-bearing oil into said mixing 6 withdrawing vapors from saidcooling zone for chamber, means for introducing said diluted oil 5effecting refrigeration, compressing, cooling and through said coolerand thence into said chilling reintroducing said vapors into saidcooling zone. chamber. means for passing a refrigerant from recoveringless volatile normally gaseous hydrosaid storage into said chillingchamber and carbons which are withdrawn in the solution of through saiddiluted oil, means for withdrawing 10 cold wax-oil slurry from thechilling zone after vapors from said chilling chamber, means for 10 theseparation of wax from diluted oil, admixing compressing and condensingsaid vapors, means further amounts of wax-bearing oil with said forintroducing said condensed vapors into said recovered hvdrocarbons,heating said diluted mixrefrigerant storage, and means for withdrawingture to eflect solution of the wax-bearing oil, chilled and dilutedwax-bearing oil from said 1 partially chilling said solution andintroducing chilling chamber. 1

said partially chilled solution into said chilling ROBERT E. WILSON.

CERTIFICATE OF CORRECTION Patent No. 2,077,656.

April 20. 19:57.

ROBERT E WILSON It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Page 2, second column, line 40, claim 1, for "diluting" readdilution; and page 3, first column, line 8, claim 7 after "volatile"insert but; and that the said Letters Patent shculd be read with thesecorrections therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 8th day of June A. D. 1937.

Henry Van Arsdale (Seali Acting Commissioner of Patents.

the use of normally gaseous hydrocarbon diluentrefrigerant mixtureswhich comprises employing separate diluent and refrigerant cycles withan evaporative cooling none common to both cycles,

8.11: a dewaxins system. a heated mixing chamber, a cooler, a chillingchamber, a refrigerant storage, means for introducing a suitable diluentand a wax-bearing oil into said mixing 6 withdrawing vapors from saidcooling zone for chamber, means for introducing said diluted oil 5effecting refrigeration, compressing, cooling and through said coolerand thence into said chilling reintroducing said vapors into saidcooling zone. chamber. means for passing a refrigerant from recoveringless volatile normally gaseous hydrosaid storage into said chillingchamber and carbons which are withdrawn in the solution of through saiddiluted oil, means for withdrawing 10 cold wax-oil slurry from thechilling zone after vapors from said chilling chamber, means for 10 theseparation of wax from diluted oil, admixing compressing and condensingsaid vapors, means further amounts of wax-bearing oil with said forintroducing said condensed vapors into said recovered hvdrocarbons,heating said diluted mixrefrigerant storage, and means for withdrawingture to eflect solution of the wax-bearing oil, chilled and dilutedwax-bearing oil from said 1 partially chilling said solution andintroducing chilling chamber. 1

said partially chilled solution into said chilling ROBERT E. WILSON.

CERTIFICATE OF CORRECTION Patent No. 2,077,656.

April 20. 19:57.

ROBERT E WILSON It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Page 2, second column, line 40, claim 1, for "diluting" readdilution; and page 3, first column, line 8, claim 7 after "volatile"insert but; and that the said Letters Patent shculd be read with thesecorrections therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 8th day of June A. D. 1937.

Henry Van Arsdale (Seali Acting Commissioner of Patents.

